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Swarm of Spiders 5e: Stats, Webs and Running the Nest
A swarm of spiders is a CR 1/2 Medium swarm of Tiny beasts with AC 12, 22 hit points, a 20-foot walk and climb speed, and a bite that deals 10 piercing damage (4d4) to a creature in its space. It is the base swarm of insects with three spider traits added: Spider Climb, Web Sense and Web Walker. On bare stone it's a modest hazard. Inside a web, where the party is stuck and the swarm moves freely, it fights far above its CR. There's no 2024 stat block for it; the 2024 Swarm of Insects with a Climb Speed takes its place.
Swarm.The swarm can occupy another creature's space and vice versa, and the swarm can move through any opening large enough for a Tiny insect. The swarm can't regain hit points or gain temporary hit points.
Spider Climb.The swarm can climb difficult surfaces, including upside down on ceilings, without needing to make an ability check.
Web Sense.While in contact with a web, the swarm knows the exact location of any other creature in contact with the same web.
Web Walker.The swarm ignores movement restrictions caused by webbing.
Actions
Bites.Melee Weapon Attack: +3 to hit, reach 0 ft., one target in the swarm's space. Hit: 10 (4d4) piercing damage, or 5 (2d4) piercing damage if the swarm has half of its hit points or fewer.
Stat block from the SRD 5.1 (2014 rules) by Wizards of the Coast, licensed under CC-BY-4.0. Check an encounter with this monster in the encounter calculator.
SRD 5.1 prints it under the swarm of insects as "Variant: Insect Swarms": the base swarm plus Spider Climb, Web Sense and Web Walker. The rest is the standard swarm package: shared spaces, no healing, resistance to bludgeoning, piercing and slashing (magic weapons too) and immunity to eight conditions, grappled and restrained included. Its bite only reaches a creature in its own space and drops to 2d4 at 11 hit points or fewer.
The Swarm of Spiders in the 2024 Rules
The 2024 SRD folds every insect swarm into one Swarm of Insects stat block whose speed reads "20 ft., Climb or Fly 20 ft. (GM's choice)". Pick Climb and it gets Spider Climb. It doesn't get Web Sense or Web Walker.
2014 Swarm of Spiders
2024 Swarm of Insects (climb)
CR (XP)
1/2 (100)
1/2 (100)
AC / HP
12 / 22
11 / 19
Climbing
Spider Climb, climb 20 ft.
Spider Climb, climb 20 ft.
Web traits
Web Sense, Web Walker
None
Bites
+3, reach 0 ft., 10 (4d4) piercing
+3, reach 5 ft., 6 (2d4 + 1) poison
If your web-nest encounter depends on the swarm moving freely through webbing, keep the 2014 block, or give the 2024 swarm Web Walker as a house rule and say so.
How Swarms of Spiders Fight
The web does the work. Web Walker means the swarm ignores movement restrictions from webbing. Web Sense means that while it touches a web, it knows the exact location of every other creature touching the same web, whether invisible, hidden or out of its 10-foot blindsight. A party that walks into a webbed corridor has given away every position.
Restrained targets are the menu. A creature restrained by webbing gives attackers Advantage. With Advantage, the swarm's +3 bite against AC 15 hits about 70% of the time instead of 45%, which raises its damage from about 4.5 to 7 a round. Restrained creatures also have Disadvantage on their own attack rolls and Dexterity saves. Two swarms crawling over a webbed fighter deal around 14 a round while the fighter struggles to break free.
Partners that make webs. The swarm can't make webs itself. Pair it with something that does:
•A giant spider (CR 1) shoots webbing that restrains on a hit, with a DC 12 Strength check to burst free.
•An ettercap (CR 2) does the same with a DC 11 check, and its 2014 stat block shares the swarm's Web Sense and Web Walker.
•A drider brings Web Walker and a lot of damage for higher-level parties.
From the ceiling. Spider Climb lets the swarm cross ceilings without a check. Let it wait above a doorway and drop onto the first character through, who now has a swarm in their space before anyone acts.
It doesn't retreat. A spider swarm has Intelligence 1. It bites until it's dead or until there's nothing left touching the web.
Running a Spider Swarm Encounter
Each swarm is worth 100 XP. Encounters for four characters:
Party
Creatures
XP
2024 difficulty
2014 DMG guideline
Level 1
1 swarm
100
Low
Easy
Level 2
1 giant spider + 2 swarms
400
Low
Deadly
Level 3
1 ettercap + 3 swarms
750
Moderate
Hard
Level 4
1 ettercap + 4 swarms
850
Low
Hard
The 2024 budget treats a web nest as a light fight. The 2014 Dungeon Master's Guide guidelines (see our encounter calculator) apply the ×2 group multiplier and rate the level 2 nest as Deadly. Trust the 2014 number if the room is full of webs. Restrained characters with Disadvantage on attacks against creatures that resist their weapons are in more trouble than the XP suggests.
How Players Beat a Swarm of Spiders
•Burn the web first. A giant spider's or ettercap's webbing is vulnerable to fire. Clearing webbing from an area takes away Web Sense and frees restrained allies. DM ruling, not rules text: a torch pressed to a web section clears it in one action; the SRD gives webbing statistics only for the strands that restrain a creature (AC 10, 5 hit points).
•Area spells.Burning Hands works twice over: 3d6 to every swarm in the cone, and the fire spreads to flammable objects. Thunderwave deals 2d8 and pushes each swarm that fails its Constitution save (+0) 10 feet away from the caster, off whoever it was eating.
•Wisdom saves. At −2, Wisdom is the swarm's weak save among the ones spells usually target. Spirit Guardians fails it 70% of the time at DC 13.
•Skip control spells. The swarm is immune to restrained, so the same webs that hold the party don't hold it, and Entangle does nothing to it.
•Leave the web. Off the web, the swarm loses its information advantage and moves at 20 feet. Characters who back out of a webbed room and fight in the bare corridor face an ordinary swarm.
Swarm of Spiders Encounter Ideas
The silk loft. A weaver's guild buys spider silk from a farmer who keeps giant spiders in an old barn. The farmer has gone quiet. The barn loft is webbed wall to wall, and two swarms hatched from an egg sac nobody noticed. The giant spiders are hungry and agitated, and the farmer is cocooned but alive on the rafters.
The rope shaft. An abandoned mine's only way down is a 60-foot shaft with a rope ladder. Halfway down, the shaft wall is thick with webbing and a swarm waits there, Web Sense telling it the moment someone grips the ladder. Fighting while climbing is miserable. Burning the web risks burning the ladder.
The webbed archive. A wizard's tower has been shut for a decade. The library is draped in old webs, and an ettercap tends three swarms among the shelves. The party needs one book from the room. Fire clears the webs and also the books.
Frequently Asked Questions
What CR is a swarm of spiders in 5e?
CR 1/2, worth 100 XP. It has AC 12, 22 hit points and a bite that deals 10 (4d4) piercing damage, or 5 (2d4) at half its hit points or fewer.
Is the swarm of spiders in the SRD?
Yes, in SRD 5.1: it's listed under Swarm of Insects as one of the insect-swarm variants. The 2024 SRD has no separate spider swarm; use the Swarm of Insects with a Climb Speed.
What does Web Sense do?
While the swarm is in contact with a web, it knows the exact location of any other creature in contact with the same web. That covers creatures that are invisible, hidden or beyond its 10-foot blindsight.
Can a swarm of spiders be restrained by webs?
No. Web Walker lets it ignore movement restrictions caused by webbing, and it is immune to the restrained condition anyway.
What's the difference between a spider swarm and a giant spider?
A giant spider is one CR 1 Large creature that shoots restraining webs and has a poison bite. A swarm of spiders is CR 1/2, can't make webs, resists weapon damage and shares spaces with its victims. They work best together: the giant spider restrains, the swarm bites with Advantage.
Stat blocks: System Reference Document 5.1 (2014), Wizards of the Coast, CC-BY-4.0. Tactics, encounter math and ideas are Loreify's own.
This page includes material from the System Reference Document 5.1 and 5.2.1 by Wizards of the Coast LLC, available under the Creative Commons Attribution 4.0 International License. Loreify is not affiliated with Wizards of the Coast.